Japanese Patent Laying-Open No. 2008-272923 (PTL 1) discloses a cutting insert that grooves, for example, a workpiece such as steel. The material for an edge portion of the cutting insert is cemented carbide. However, the use of cemented carbide easily welds the workpiece to a blade tip. This leads to a shorter lifetime of the cutting insert, so that the workpiece cannot have good surface quality.
Japanese Patent Laying-Open No. 7-314204 (PTL 2) discloses a cutting insert, where the material for an edge portion is a diamond sintered compact and the material for a substrate holding the edge portion is cemented carbide. Changing the material for the edge portion from cemented carbide to diamond sintered compact can significantly reduce welding of a workpiece to the edge portion. However, diamond is difficult to process because it is a material with very high hardness which easily chips. The cutting insert thus has a breaker wall provided in the substrate, not in the edge portion.